Flow meters are meters designed to measure the flow of a fluid/gas in a wide variety of applications. The most common types of meters presently used to meter fluid/gas flow are the positive displacement meter, the current meter (e.g. a turbine meter), and the compound meter.
Positive displacement flowmeters operate by repeatedly filling and emptying compartments of known volume with the liquid or gas from the flow stream. The flow rate calculation is based on the number of times these compartments are filled and emptied. Positive displacement meters are more accurate than current meters in low flow rates applications, and thus, are widely used to measure commodity consumption in municipal and industrial gas applications, municipal water applications, oil/refined fuel applications (e.g. the measurement of the transfer of refined fuels as well as the use of petroleum products) and industrial applications (e.g. the measure of liquids other than water or petroleum products in industrial and process plants which may include some water measurement for non-billing purposes).
In contrast, current meters (hereafter referred to as turbine meters) are used when the line sizes are larger and the flow volume is greater than can be handled by positive displacement meters. Turbine meters are most accurate in medium to high flow rate and high flow volume applications. Consequently, turbine meters are often used in the larger line sizes, especially those exceeding four inches.
Compound meters and Combo meters are more difficult to classify as they are actually a hybrid meter. Compound meters typically comprise both a positive displacement meter and a turbine meter. Compound meters are generally used to meter fluid flow in an installation where demand varies considerably between high demand and low demand. For example, municipal water utilities may use a compound meter to meter the water consumption of a large apartment complex, where water flow rates are generally high in the morning and evening while being much lower during the day (when most people are at work) and at night (when most people sleep). Such prior art meters are disclosed by Zellering in U.S. Pat. No. 5,698,781, by Bradham III, et al. in U.S. Pat. Nos. 4,100,799, and 4,175,434 and such patents are incorporated by this reference for all purposes.
As the name implies, a compound meter comprises two or more measuring chambers (typically two) in a single meter body. A low flow chamber housing a positive displacement meter (for example) may be used to measure fluid flow at low flow rates while a second high flow rate chamber housing a turbine meter may be used to measure fluid flow at higher flow rates. Similarly, a combo meter comprises two or more measuring chambers connected in parallel, typically in two different meter bodies. One measuring chamber is configured for a high flow rate while a second measuring chamber is configured for a relatively low flow rate. A check valve typically is placed in the high flow path of the turbine meter where such check valve is designed to open only when a predefined flow rate or pressure is achieved. When such check valve is closed, all fluid flow is diverted through the low flow chamber where the flow rate is measured by a low flow rate meter. If and when the fluid's flow rate reaches a predefined value, the check valve will open allowing fluid flow through the high flow chamber where the flow rate is measured by the turbine meter.
In many prior art compound meters, the check valve has been integrated into the water meter housing. These prior art check valves often comprise a “clapper” connected to pins and rollers that must be precisely calibrated so that the clapper mates against a seal (or seat) within the meter to prevent fluid flow until the predefined flow rate/pressure is achieved. Thus, if the rollers/pins in such prior art meter become worn to the point their operation (calibration) is affected, or the seal becomes worn to the point water leaks around the clapper when the check valve is closed, a compound meter will not accurately meter fluid flow rates. Indeed, when such compound meters are used as revenue meters by water utilities, such water utilities typically require annual testing of the check valve operation to verify that it is operating properly. Similarly, for some prior art meters, utilities require annual examination, and sometimes annual replacement, of the check valve seal.
The check valve assemblies and check valve seals in many prior art compound meters are very complicated to repair or replace. In some meters, to access a check valve, the heavy metal turbine chamber housing the compound meter must be removed from the fluid delivery system and the turbine metering element removed from the meter housing to get to the check valve components. In other meters, the repair person must disconnect the check valve side of the compound meter from the fluid delivery system and stick his hands inside the pipe, use tools to disconnect various parts of the check valve assembly, or perhaps the entire turbine meter, and remove the check valve assembly and perhaps the turbine meter. Such tasks require the ability to move heavy objects and must typically be performed in environments that are limited in space.
For the reasons described above, recalibration/replacement of a check valve assembly or inspecting/changing a check valve seal is often an arduous task requiring many hours to complete, and must typically be performed by trained personnel with the ability to move heavy objects. As a result, when repair or replacement of a check valve in prior art compound meter becomes necessary, many owners of such compound meters have found that scrapping a perfectly repairable compound meter is a better solution than investing the time and money required to repair the meter.
Therefore, there is a need for a compound meter having a check valve assembly module (1) that can easily be removed from the compound meter without having to remove the metering module, (2) that has few or no complicated rollers and pins that require calibration, (3) that requires little or no special training to remove, (4) that does not require the meter repairperson to move the relatively heavy compound meter, (5) that may comprise a seal as part of the check valve assembly simplifying seal inspection, removal and replacement; and (6) in which all meter components are secured in their respective chambers within meter using only external fasteners.
Another problem with prior art compound meters concerns safety issues related to testing the check valve for proper operation. As noted above, if the check valve in a compound meter is not working properly such compound meter will not meter flow rate accurately. Thus, many owners of compound meters require periodic (e.g. annual) testing of the check valve. To facilitate testing of the check valve assembly, an access point to the fluid flowing through the check valve assembly is often provided. Such access point is located between the check valve and the meter output (i.e. on the customer side of the meter) and is normally terminated with a plug to seal the access point when not in use. When the check valve is to be tested, the plug is removed from the access point and test equipment attached to the access point to determine the pressure required to open the check valve. Notably, in compound water meters, the pressure the fluid exerts against the plug may be between 150 pounds/in2 to 300 pounds/in2. Therefore, the flow of fluid through the meter must be turned off before attaching the test equipment. Should the test personnel mistakenly remove the plug under pressure, however, the plug becomes a projectile capable of seriously injuring persons in the vicinity of the meter. Consequently, there is a need for a compound fluid meter that has built in test connections and pressure indicators that provide improved safety conditions for test personnel.
Still another problem that needs to be addressed relates to the complicated check valve assemblies associated with compound meters currently installed in metering applications. Such meters typically require annual testing, calibration and seal inspection. Examples of prior art compound/combo flow meters include Schwartz et al., U.S. Pat. No. 6,581,457, Kullmann et al., U.S. Pat. No. 4,429,571, Bradham, II et al., U.S. Pat. No. 4,100,799, Zellering et al., U.S. Pat. No. 5,698,781, and Schloetterer et al., U.S. Pat. No. 5,831,158 and such patents are incorporated by this reference for all that they disclose. As previously described, for many prior art compound/combo meters, when repair or replacement of a check valve becomes necessary, the owners of such compound/combo meters may find that scraping a perfectly repairable compound meter is a better solution than investing the time and money required to repair the meter. Consequently, there is a need for a check valve module that can be installed into existing meters thereby replacing the original check valve assembly that (1) can be easily removed from the compound meter without having to remove the metering module (2) has few or no complicated rollers and pins that require calibration, (3) requires little special training to remove, (4) does not require the meter repairperson to move relatively heavy objects such as the compound meter, and (5) may comprise a seal as part of the check valve assembly simplifying seal inspection, removal and replacement.
Yet another problem that needs to be addressed concerns prior art water meters that comprises components constructed of lead. Epidemiological studies reported by the Centers for Disease Control (CDC) note that harmful effects of lead in children can be observed at blood lead levels at least as low as 10 micrograms of lead per deciliter of blood (ug/dL). Notably, drinking water is one possible source of lead exposure. Consequently, actions have been taken by water utilities, government regulators, and manufacturers to minimize lead in drinking water.
Wile there are numerous possible sources of lead exposure, and while the relative contribution to total lead exposure from drinking water is typically low compared to other sources of lead exposure, water utilities are becoming increasingly sensitive to possible sources of lead contamination in their water system. Lead in drinking water is most commonly caused by corrosion of the water delivery system. Interior surfaces of faucets, fixtures, pipe, fittings, valves, solder used to join copper pipe, and water meters may be made of brass, bronze, or other materials that contain lead. For water distribution systems in general, and water meters specifically, during periods when water sits in a distribution system, lead may leach into the drinking water. Thus, water utilities have began requiring new water meters to be constructed of components that are substantially free of lead. However, millions of prior art water meters comprised of components containing significant amounts of lead are already installed in water distribution systems. Consequently, there is a need for an apparatus and method for cost effectively upgrading such prior art water meters with lead free components.
Another problem that needs to be addressed is “water hammer” (fluid hammer). Fluid hammer is a pressure shock/energy wave induced in plumbing supply systems whenever there is a sudden change in the steady state condition of a non-compressible liquid such as water. Pumps, valves, faucets, toilets, and fast solenoid-activated valves (such as commonly found in washing machines and dishwashers) are all examples of devices that can induce water hammer within a typical plumbing system. Fluid hammer can also be caused by the rapid closure of a check valve (check valve slam).
Water hammer (or, more generally, fluid hammer) is a pressure surge or wave caused by the kinetic energy of a fluid in motion when it is forced to stop or change direction suddenly. When a check valve slams shut at one end of a fluid delivery system, an energy wave is generated and propagates through the system. In domestic plumbing system such energy waves can often cause a loud banging noise resembling a hammering noise. If such energy wave is strong enough, extreme damage to the fluid delivery system (such as exploding and imploding pipes) may result.
Some prior art attempts to prevent or dampen fluid hammer include using hydro-pneumatic devices (such as a water hammer arrestor) that absorb the energy wave, use of slow closing valves and using high quality but expensive pipes, install pipe risers inside the wall at each faucet or valve junction.
Such prior art methods may work well for their purposes but in flow meters the check valve needs to close as quickly as possible. Thus, there is a need for a check valve module that closes quickly while providing a method of safely dissipating the energy contain in a fluid hammer energy wave.